U.S. patent application number 15/740644 was filed with the patent office on 2018-07-12 for modified diene elastomer with reduced pdi and composition containing same.
This patent application is currently assigned to COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN. The applicant listed for this patent is COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN. Invention is credited to Marie-Helene DESSENDIER, Charlotte DIRE, Margarita DORATO, Jean Marc MARECHAL, Florent VAULTIER.
Application Number | 20180194866 15/740644 |
Document ID | / |
Family ID | 54356481 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180194866 |
Kind Code |
A1 |
DESSENDIER; Marie-Helene ;
et al. |
July 12, 2018 |
MODIFIED DIENE ELASTOMER WITH REDUCED PDI AND COMPOSITION
CONTAINING SAME
Abstract
A modified diene elastomer is provided. The elastomer comprises:
at least 70% by weight, with respect to the total weight of the
modified diene elastomer, of a linear diene elastomer
functionalized predominantly in the middle of the chain by an
alkoxysilane group, optionally partially or completely hydrolysed
to give silanol, the alkoxysilane group optionally bearing another
functional group capable of interacting with a reinforcing filler,
the alkoxysilane group bonded to the two branches of the diene
elastomer via the silicon atom, the functionalized diene elastomer
exhibiting a polydispersity index before fractionalization of less
than or equal to 1.6; and more than 0 and up to 30% by weight, with
respect to the total weight of the modified diene elastomer, of a
star-branched diene elastomer exhibiting a polydispersity index
before star-branching of less than or equal to 1.6, the Mooney
viscosity of the modified diene elastomer varying from 30 to
80.
Inventors: |
DESSENDIER; Marie-Helene;
(Clermont-Ferrand Cedex 09, FR) ; DIRE; Charlotte;
(Clermont-Ferrand Cedex 09, FR) ; DORATO; Margarita;
(Clermont-Ferrand Cedex 09, FR) ; MARECHAL; Jean
Marc; (Clermont-Ferrand Cedex 09, FR) ; VAULTIER;
Florent; (Clermont-Ferrand Cedex 09, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMPAGNIE GENERALE DES ETABLISSEMENTS MICHELIN |
Clermont-Ferrand |
|
FR |
|
|
Assignee: |
COMPAGNIE GENERALE DES
ETABLISSEMENTS MICHELIN
Clermont-Ferrand
FR
|
Family ID: |
54356481 |
Appl. No.: |
15/740644 |
Filed: |
July 1, 2016 |
PCT Filed: |
July 1, 2016 |
PCT NO: |
PCT/EP2016/065592 |
371 Date: |
December 28, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 3/36 20130101; C08K
5/31 20130101; C08L 2205/025 20130101; C08K 3/06 20130101; C08K
5/548 20130101; C08K 5/09 20130101; C08K 5/18 20130101; C08C 19/22
20130101; C08C 19/25 20130101; C08L 2312/02 20130101; C08L 47/00
20130101; C08K 3/22 20130101; C08C 19/00 20130101; C08L 15/00
20130101; C08L 9/06 20130101; C08C 19/44 20130101; B60C 1/0016
20130101; C08L 15/00 20130101; C08L 15/00 20130101; C08L 47/00
20130101; C08K 3/36 20130101; C08K 5/548 20130101; C08K 5/09
20130101; C08K 3/22 20130101; C08K 5/18 20130101; C08K 5/31
20130101; C08K 3/06 20130101 |
International
Class: |
C08C 19/25 20060101
C08C019/25; C08C 19/00 20060101 C08C019/00; C08L 9/06 20060101
C08L009/06; B60C 1/00 20060101 B60C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 2015 |
FR |
1556253 |
Claims
1. A modified diene elastomer comprising: a) at least 70% by
weight, with respect to the total weight of the modified diene
elastomer, of a linear diene elastomer functionalized predominantly
in the middle of the chain by an alkoxysilane group, optionally
partially or completely hydrolysed to give silanol, the
alkoxysilane group optionally bearing another functional group
capable of interacting with a reinforcing filler, the alkoxysilane
group being bonded to the two branches of the diene elastomer via
the silicon atom, the functionalized diene elastomer exhibiting a
polydispersity index before functionalization of less than or equal
to 1.6, b) more than 0 and up to 30% by weight, with respect to the
total weight of the modified diene elastomer, of a star-branched
diene elastomer exhibiting a polydispersity index before
star-branching of less than or equal to 1.6, the Mooney viscosity
of the modified diene elastomer varying from 30 to 80.
2. A modified diene elastomer according to claim 1, wherein the
other functional group capable of interacting with a reinforcing
filler of the diene elastomer a) is a functional group chosen from
primary, secondary or tertiary and cyclic or non-cyclic amines,
isocyanates, imines, cyanos, thiols, carboxylates, epoxides and
primary, secondary or tertiary phosphines.
3. A modified diene elastomer according to claim 1, wherein the
functional group capable of interacting with a reinforcing filler
of the diene elastomer a) is a tertiary amine functional group.
4. A modified diene elastomer according to claim 1, wherein the
functional group capable of interacting with a reinforcing filler
of the diene elastomer a) and the silicon atom bonded to the
elastomer are connected to one another via a spacer group defined
as being a saturated or unsaturated, cyclic or non-cyclic, linear
or branched, divalent C.sub.1-C.sub.18 aliphatic hydrocarbon
radical or a divalent C.sub.6-C.sub.18 aromatic hydrocarbon
radical, the spacer group optionally comprising one or more
aromatic radicals and/or one or more heteroatoms.
5. A modified diene elastomer according to claim 1, wherein the
spacer group of the diene elastomer a) is a linear divalent
C.sub.1-C.sub.5 aliphatic hydrocarbon radical.
6. A modified diene elastomer according to claim 1, wherein the
alkoxysilane group is a methoxysilane or ethoxysilane group,
optionally partially or completely hydrolysed to give silanol.
7. A modified diene elastomer according to claim 1, wherein the
modified diene elastomer comprises at least 80% by weight, with
respect to the total weight of the modified diene elastomer, of the
linear diene elastomer functionalized predominantly in the middle
of the chain a).
8. A modified diene elastomer according to claim 1, wherein the
modified diene elastomer comprises at most 20% by weight, with
respect to the total weight of the modified diene elastomer, of the
star-branched diene elastomer b).
9. A modified diene elastomer according to claim 1, wherein the
star-branched diene elastomer is a tin-based or silicon-based
star-branched elastomer.
10. A modified diene elastomer according to claim 1, wherein the
star-branched diene elastomer b) is a star-branched diene elastomer
comprising three or four branches.
11. A modified diene elastomer according to claim 1, wherein the
diene elastomer is a copolymer of butadiene and of a vinylaromatic
monomer.
12. A modified diene elastomer according to claim 1, wherein the
diene elastomers a) and b) have, before functionalization and
star-branching, the same microstructure and the same
macrostructure.
13. A reinforced rubber composition based on at least one
reinforcing filler and on an elastomer matrix comprising at least
one modified diene elastomer as defined in claim 1.
14. A composition according to claim 13, wherein the reinforcing
filler(s) comprise(s) more than 50% by weight, with respect to the
total weight of the reinforcing filler(s), of reinforcing inorganic
filler.
15. A composition according to claim 13, wherein the reinforcing
inorganic filler consists of silica.
16. A semi-finished article made of rubber for a tire, wherein the
rubber comprises a crosslinkable or crosslinked rubber composition
according to claim 13.
17. A semi-finished article according to claim 16, wherein the
article is a tread.
18. A tire comprising a semi-finished article as defined in claim
17.
Description
[0001] This application is a 371 national phase entry of
PCT/EP2016/065592, filed 1 Jul. 2016, which claims benefit of
French Patent Application No. 1556253, filed 2 Jul. 2015, the
entire contents of which are incorporated herein by reference for
all purposes.
BACKGROUND
1. Technical Field
[0002] The invention relates to a modified diene elastomer
comprising at least 70% by weight of a specific linear diene
elastomer functionalized predominantly in the middle of the chain
by an alkoxysilane group, optionally partially or completely
hydrolysed, bearing, if appropriate, another functional group
capable of interacting with a reinforcing filler within a rubber
composition, and at most 30% by weight of a specific star-branched
diene elastomer, the Mooney viscosity of the modified diene
elastomer varying from 30 to 80.
2. Related Art
[0003] Now that savings in fuel and the need to protect the
environment have become a priority, it is desirable to produce
mixtures having a hysteresis which is as low as possible in order
to be able to process them in the form of rubber compositions which
can be used in the manufacture of various semi-finished products
participating in the composition of tire casings, such as, for
example, underlayers, sidewalk or treads, and in order to obtain
tires having a reduced rolling resistance.
[0004] The reduction in the hysteresis of the mixtures is an
ongoing objective which has, however, to be done while retaining
the suitability for processing, in particular in the raw state, of
the mixtures, while at the same time maintaining the resistance to
flow of the elastomers.
[0005] Many solutions have already been experimented with in order
to achieve the objective of a fall in hysteresis. Mention may in
particular be made of the modification of the structure of diene
polymers and copolymers at the end of polymerization by means of
functionalization agents, coupling agents or star-branching agents
with the aim of obtaining a good interaction between the polymer,
thus modified, and the filler, whether this is carbon black or a
reinforcing inorganic filler.
[0006] In the context of mixtures containing a reinforcing
inorganic filler, it has been proposed to use diene copolymers
functionalized by alkoxysilane derivatives.
[0007] Mention may be made, by way of illustration of this prior
art, for example, of U.S. Pat. No. 5,066,721, which describes a
rubber composition comprising a diene polymer functionalized by an
alkoxysilane having at least one non-hydrolysable alkoxyl residue
as a mixture with silica. Mention may also be made of Patent
Application EP A 0 299 074, which describes functionalized polymers
comprising alkoxysilane functional groups at the chain end. These
functionalized polymers have been described in the prior art as
effective in reducing hysteresis and improving abrasion resistance;
however, their properties remain insufficient to allow the
processing of these polymers in compositions intended to constitute
treads of tires.
[0008] Provision has also been made to combine the
functionalization by alkoxysilane functional groups with
functionalization by other functional groups, in particular amine
functional groups. Thus, Patent EP 0 992 537 describes a rubber
composition which comprises an extended elastomer functionalized at
the chain end by an alkoxysilane functional group and bearing, at
the other end or along its chain, one or more amine functional
groups. Furthermore, provision has also been made to improve the
properties of rubber compositions by using elastomers
functionalized at the chain end by alkoxysilane functional groups
bearing an amine group, whether this is as black, silica or hybrid
mixture. Mention may be made, for example, of Patent Application US
2005/0203251, which describes a rubber composition reinforced by
silica comprising an elastomer functionalized at the chain end by
an alkoxysilane bearing an amine group. Nevertheless, it turns out
that the compositions comprising elastomers thus functionalized,
whether black, silica or hybrid mixtures, do not always exhibit a
processing which is acceptable and a hysteresis which is
satisfactory for use as tire tread.
[0009] The Applicant Companies have described, in the document WO
2009133068 A1, a functionalized diene elastomer essentially
composed of the coupled entity of an elastomer having, within the
chain, a group bearing an alkoxysilane functional group and an
amine functional group, the silicon atom of this group bonding the
two parts of the diene elastomer chain. This functionalized
elastomer confers improved mechanical and dynamic properties on the
composition in which it is present, in particular an improved
hysteresis, while retaining a satisfactory raw processing, for the
purpose in particular of use as tire tread.
[0010] It is an ongoing concern of designers of materials intended
for the manufacture of tires to improve the compromise in
mechanical and dynamic properties of the rubber compositions for
the purpose of improving the performance of the tire in which they
are present, without, however, damaging the stages of its
manufacture or the properties of the elastomer. Thus, for example,
the improvement in the compromise in properties must not be made to
the detriment of the flow of the elastomer, which causes major
disadvantages during the transportation and storage of rubbers.
[0011] Provision has been made in the past to add elastomers
coupled or star-branched using additional coupling or
star-branching agents comprising tin or silicon in order to limit
the flow. Thus, for example, Patent Application WO 2009/077837
describes elastomers functionalized at each chain end in
combination with elastomers which are star-branched, particularly
by silicon. However, the combinations illustrated result in a
reinforced rubber composition, the processing/hysteresis compromise
of which is not satisfactory for a tire application. The Applicant
Companies have furthermore described, in Patent Application WO
2011/042507, a functionalized diene elastomer composed of a diene
elastomer functionalized at one chain end by a silanol functional
group and, in a certain proportion, of a coupled or star-branched
diene elastomer based on tin. This elastomer confers, on a rubber
composition in which it is present, hysteresis and processing
properties which are satisfactory and acceptable for tire use,
while exhibiting a significantly improved resistance to flow.
SUMMARY
[0012] The technical problem which the invention intends to solve
is that of further improving the compromise in hysteresis and
processing properties of a rubber composition for the purpose of a
tire application, without damaging its manufacture or the
properties of the elastomer present in this composition, in
particular its resistance to flow.
[0013] This aim is achieved in that the inventors have just
discovered, surprisingly, during their research studies, that a
modified diene elastomer comprising at least 70% by weight, with
respect to the total weight of the modified diene elastomer, of a
linear diene elastomer functionalized predominantly in the middle
of the chain by an alkoxysilane group, optionally partially or
completely hydrolysed to give silanol, the alkoxysilane group
optionally beating another functional group capable of interacting
with a reinforcing filler, the alkoxysilane group being bonded to
the two branches of the diene elastomer via the silicon atom, the
functionalized elastomer exhibiting a narrow molecular weight
distribution before functionalization, and at most 30% by weight,
with respect to the total weight of the modified diene elastomer,
of a star-branched diene elastomer exhibiting a narrow molecular
weight distribution before star-branching, the Mooney viscosity of
the modified diene elastomer varying from 30 to 80, confers, on the
rubber compositions containing it, an improvement in the raw
processing/hysteresis compromise while keeping intact the
resistance to flow of the elastomer.
[0014] A subject-matter of the invention is thus a modified diene
elastomer comprising:
[0015] a) at least 70% by weight, with respect to the total weight
of the modified diene elastomer, of a linear diene elastomer
functionalized predominantly in the middle of the chain by an
alkoxysilane group, optionally partially or completely hydrolysed
to give silanol, the alkoxysilane group optionally bearing another
functional group capable of interacting with a reinforcing filler,
the alkoxysilane group being bonded to the two branches of the
diene elastomer via the silicon atom, the functionalized diene
elastomer exhibiting a polydispersity index before
functionalization of less than or equal to 1.6, preferably ranging
from 1.2 to 1.6,
[0016] b) more than 0 and up to 30% by weight, with respect to the
total weight of the modified diene elastomer, of a star-branched
diene elastomer exhibiting a polydispersity index before
star-branching of less than or equal to 1.6, preferably ranging
from 1.2 to 1.6,
[0017] the Mooney viscosity of the modified diene elastomer varying
from 30 to 80.
[0018] A further subject-matter of the invention is a reinforced
rubber composition based on at least one reinforcing filler and on
an elastomer matrix comprising at least the modified diene
elastomer.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0019] In the present description, unless expressly indicated
otherwise, all the percentages (%) shown are % by weight.
Furthermore, any interval of values denoted by the expression
"between a and b" represents the range of values extending from
more than a to less than b (that is to say, limits a and b
excluded), whereas any interval of values denoted by the expression
"from a to b" means the range of values extending from a up to b
(that is to say, including the strict limits a and b).
[0020] The expression composition "based on" should be understood
as meaning a composition comprising the mixture and/or the reaction
product of the various constituents used, some of these base
constituents being capable of reacting, or intended to react, with
one another, at least in part, during the various phases of
manufacture of the composition, in particular during the
crosslinking or vulcanization thereof.
[0021] In the present patent application, the term "predominantly"
or "predominant", in connection with a compound, is understood to
mean that this compound is predominant among the compounds of the
same type in the composition, that is to say that it is the one
which represents the biggest fraction by weight among the compounds
of the same type. Thus, a "predominant" functional entity of a
functionalized diene elastomer is that representing the biggest
fraction by weight among the functionalized entities constituting
the diene elastomer, with respect to the total weight of the
functionalized diene elastomer. In a system comprising just one
compound of a certain type, the latter is predominant within the
meaning of the present invention.
[0022] In the present description, the term "modified diene
elastomer" is understood to mean a diene elastomer which comprises
a group comprising one or more heteroatoms.
[0023] This group can be located at the linear main elastomer chain
end. It will then be said that the diene elastomer is
functionalized at the chain end. It is generally an elastomer
obtained by reaction of a living elastomer with a functionalization
agent, that is to say any at least monofunctional molecule, the
functional group being any type of chemical group known by a person
skilled in the art to react with a living chain end.
[0024] This group can be located in the linear main elastomer
chain. It will then be said that the diene elastomer is coupled or
alternatively functionalized in the middle of the chain, in
contrast to the position "at the chain end", although the group is
not located precisely at the middle of the elastomer chain. It is
generally an elastomer obtained by reaction of a living elastomer
with a coupling agent, that is to say any at least difunctional
molecule, the functional group being any type of chemical group
known by a person skilled in the art to react with a living chain
end.
[0025] This group can be central, to which n elastomer chains
(n>2) are bonded, forming a star-branched structure. It will
then be said that the diene elastomer is star-branched. It is
generally an elastomer obtained by reaction of a living elastomer
with a star-branching agent, that is to say any polyfunctional
molecule, the functional group being any type of chemical group
known by a person skilled in the art to react with a living chain
end.
[0026] A person skilled in the art will understand that a
functionalization reaction with an agent comprising more than one
functional group which is reactive with regard to the living
elastomer results in a mixture of entities functionalized at the
chain end and in the middle of the chain, constituting the linear
chains of the functionalized elastomer, and also, if appropriate,
star-branched entities. Depending on the operating conditions,
mainly the molar ratio of the functionalization agent to the living
chains, certain entities are predominant in the mixture.
[0027] The term "diene elastomer" should be understood, in a known
way, as meaning an (one or more is understood) elastomer resulting
at least in part (i.e., a homopolymer or a copolymer) from diene
monomers (monomers bearing two conjugated or non-conjugated
carbon-carbon double bonds). More particularly, diene elastomer is
understood as meaning any homopolymer obtained by polymerization of
a conjugated diene monomer having from 4 to 12 carbon atoms or any
copolymer obtained by copolymerization of one or more conjugated
dienes with one another or with one or more vinylaromatic compounds
having from 8 to 20 carbon atoms. In the case of copolymers, the
latter contain from 20% to 99% by weight of diene units and from 1%
to 80% by weight of vinylaromatic units.
[0028] The following in particular are suitable as conjugated
dienes which can be used in the process in accordance with the
invention: 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C.sub.1 to
C.sub.5 alkyl)-1,3-butadienes, such as, for example,
2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl
-3-ethyl-1,3-butadiene or 2-methyl-3-isopropyl-1,3-butadiene,
phenyl-1,3-butadiene, 1,3-pentadiene and 2,4-hexadiene, and the
like.
[0029] The following in particular are suitable as vinylaromatic
compounds: styrene, ortho-, meta- or para-methylstyrene, the
"vinyltoluene" commercial mixture, para-(tert-butyl)styrene,
methoxystyrenes, vinylmesitylene, divinylbenzene and
vinylnaphthalene, and the like.
[0030] The diene elastomer is preferably selected from the group of
highly unsaturated diene elastomers consisting of polybutadienes
(BRs), synthetic polyisoprenes (IRs), butadiene copolymers, in
particular copolymers of butadiene and of a vinylaromatic monomer,
isoprene copolymers and the mixtures of these elastomers. Such
copolymers are more particularly butadiene/styrene copolymers
(SBRs), isoprene/butadiene copolymers (BIRs), isoprene/styrene
copolymers (SIRs) and isoprene/butadiene/styrene copolymers
(SBIRs). Among these copolymers, butadiene/styrene copolymers
(SBRs) are particularly preferred.
[0031] The diene elastomer can have any microstructure which
depends on the polymerization conditions used. The elastomer can be
a block, statistical, sequential or microsequential elastomer, and
the like, and can be prepared in dispersion or in solution. When an
anionic polymerization is concerned, the microstructure of these
elastomers can be determined by the presence or absence of a
randomizing agent and the amounts of randomizing agent
employed.
[0032] The term "polydispersity index" is understood to mean,
within the meaning of the invention, the weight-average molecular
weight/number-average molecular weight ratio. The weight-average
and number-average molecular weights are measured by size exclusion
chromatography.
[0033] The term "linear diene elastomer functionalized
predominantly in the middle of the chain", i.e. the elastomer a),
is understood to mean, according to the invention, the mixture of
the linear entities of the functionalized elastomer, namely the
linear chains functionalized at the chain end and the linear chains
functionalized in the middle of the chain, the latter being
predominant by weight in this mixture and preferably representing
at least 50%, indeed even at least 70%, by weight of this
mixture.
[0034] According to a preferred embodiment, the modified diene
elastomer according to the invention comprises at least 80% by
weight, with respect to the total weight of the modified diene
elastomer, of the linear diene elastomer functionalized
predominantly in the middle of the chain a).
[0035] According to another preferred embodiment, the modified
diene elastomer according to the invention comprises at most 20% by
weight, with respect to the total weight of the modified diene
elastomer, of the star-branched diene elastomer b).
[0036] According to a particularly preferred embodiment, the
modified diene elastomer according to the invention comprises at
least 80% by weight, with respect to the total weight of the
modified diene elastomer, of the linear diene elastomer
functionalized predominantly in the middle of the chain a) and at
most 20% by weight, with respect to the total weight of the
modified diene elastomer, of the star-branched diene elastomer
b).
[0037] According to an alternative form of the invention, the diene
elastomer a) does not comprise another functional group than that
comprising the silicon atom directly bonded to the elastomer chain
(that is to say, the alkoxysilane group).
[0038] According to another alternative form of the invention, the
diene elastomer a) also comprises another functional group capable
of interacting with a reinforcing filler, this functional group
advantageously being borne by the silicon of the alkoxysilane
group, directly or via a spacer group. This alternative form is
understood as not excluding the fact that the alkoxysilane group
comprising the silicon atom directly bonded to the elastomer chain
interacts favourably with the reinforcing filler.
[0039] The term "alkoxysilane group interacting favourably with the
reinforcing filler" or "functional group capable of interacting
with a reinforcing filler" is understood to mean any alkoxysilane
group or functional group capable of forming, within a rubber
composition reinforced by means of a filler, a physical or chemical
bond with the filler. This interaction can be established, for
example, via covalent, hydrogen, ionic and/or electrostatic bonds
between the functional group and functional groups present on
fillers.
[0040] The alkoxy radical of the alkoxysilane group can be of
formula R'O--, where R' represents a substituted or unsubstituted
C.sub.1-C.sub.10, indeed even C.sub.1-C.sub.8, alkyl group,
preferably a C.sub.1-C.sub.4 alkyl group, more preferably methyl
and ethyl.
[0041] The term "functional group capable of interacting with a
reinforcing filler" is preferably understood to mean functional
groups comprising at least one heteroatom chosen from N, S, O or P.
Mention may be made, by way of example, among these functional
groups, of primary, secondary or tertiary and cyclic or non-cyclic
amines, isocyanates, imines, cyanos, the thiol functional group,
carboxylates, epoxides and primary, secondary or tertiary
phosphines.
[0042] Mention may thus be made, as secondary or tertiary amine
functional group, of amines substituted by C.sub.1-C.sub.10,
preferably C.sub.1-C.sub.4, alkyl radicals, more preferably a
methyl or ethyl radical, or else cyclic amines forming a
heterocycle comprising a nitrogen atom and at least one carbon
atom, preferably from 2 to 6 carbon atoms. For example, the
methylamino-, dimethyl amino-, ethylamino-, diethylamino-,
propylamino-, dipropylamino-, butylamino-, pentylamino-,
dipentylamino-, hexylamino-, dihexylamino- or
hexamethyleneamino-groups, preferably the diethylamine- and
dimethylamino-groups, are suitable.
[0043] Mention may be made, as imine functional group, of the
ketimines. For example, the (1,3-dimethylbutylidene)amino-,
(ethylidene)amino-, (1-methylpropylidene)amino-,
(4-N,N-dimethylaminobenzylidene)amino-, (cyclohexylidene)amino-,
dihydroimidazole and imidazole groups are suitable.
[0044] Mention may be made, as carboxylate functional group, of
acrylates or methacrylates. Such a functional group is preferably a
methacrylate.
[0045] Mention may be made, as epoxide functional group, of the
epoxy or glycidyloxy groups.
[0046] Mention may be made, as secondary or tertiary phosphine
functional group, of phosphines substituted by C.sub.1-C.sub.10,
preferably C.sub.1-C.sub.4, alkyl radicals, more preferably a
methyl or ethyl radical, or else diphenylphosphine. For example,
the methylphosphino-, dimethylphosphino-, ethylphosphino-,
diethylphosphino, ethylmethylphosphino- and
diphenylphosphino-groups are suitable.
[0047] Preferably, the functional group capable of interacting with
a reinforcing filler of the diene elastomer a) is a tertiary amine
functional group, preferably a diethylamine or dimethylamine
functional group.
[0048] According to an alternative form of the invention, the other
functional group capable of interacting with a reinforcing filler
is directly bonded to the silicon atom itself directly bonded to
the diene elastomer.
[0049] According to another alternative form of the invention, the
other functional group capable of interacting with a reinforcing
filler and the silicon atom bonded to the diene elastomer are
connected together by a spacer group which can be an atom or a
group of atoms. The spacer group can be a saturated or unsaturated,
cyclic or non-cyclic, linear or branched, divalent C.sub.1-C.sub.18
aliphatic hydrocarbon radical or a divalent C.sub.6-C.sub.18
aromatic hydrocarbon radical and can comprise one or more aromatic
radicals and/or one or more heteroatoms. The hydrocarbon radical
can optionally be substituted.
[0050] According to a preferred alternative form of the invention,
the spacer group is a linear or branched, divalent C.sub.1-C.sub.10
aliphatic hydrocarbon radical, more preferably a linear divalent
C.sub.1-C.sub.5 aliphatic hydrocarbon radical and more preferably
still the linear divalent C.sub.3 hydrocarbon radical.
[0051] The different aspects, preferred or nonpreferred, which
precede and which relate in particular to the nature of the other
functional group capable of interacting with a reinforcing filler,
the nature of the spacer group, the nature of the alkoxysilane
group and the nature of the diene elastomer can be combined with
one another.
[0052] According to advantageous alternative forms of the
invention, at least one of the four following characteristics is
observed and preferably the four:
[0053] the other functional group capable of interacting with a
reinforcing filler is a tertiary amine, more particularly a
diethylamine- or dimethylamino-group,
[0054] the spacer group is a linear C.sub.1-C.sub.5 hydrocarbon
radical, more preferably still the linear C.sub.3 hydrocarbon
radical,
[0055] the functional group comprising the silicon atom is a
methoxysilane or ethoxysilane, optionally partially or completely
hydrolysed to give silanol,
[0056] the diene elastomer is a butadiene/styrene copolymer.
[0057] The star-branched diene elastomer b) is preferably a
tin-based or silicon-based star-branched diene elastomer.
[0058] The star-branched diene elastomer b) is preferably a
star-branched diene elastomer comprising three or four
branches.
[0059] The diene elastomer functionalized in the middle of the
chain a) and the star-branched diene elastomer b) can have, before
functionalization and star-branching, the same microstructure or a
different microstructure.
[0060] Preferably, the linear diene elastomer functionalized
predominantly in the middle of the chain a) and the star-branched
diene elastomer b) have, before functionalization and
star-branching, the same microstructure.
[0061] Preferably again, the linear diene elastomer functionalized
predominantly in the middle of the chain a) and the star-branched
diene elastomer b) have, before functionalization and
star-branching, the same microstructure and the same
macrostructure.
[0062] The modified diene elastomer according to the invention can
be obtained by means of a process as described below.
[0063] The first stage of a process for the preparation of the
modified diene elastomer is the anionic polymerization of at least
one conjugated diene monomer in the presence of a polymerization
initiator.
[0064] Use may be made, as polymerization initiator, of any known
monofunctional anionic initiator. However, an initiator comprising
an alkali metal, such as lithium, is preferably used.
[0065] Those comprising a carbon-lithium bond are suitable in
particular as organolithium initiators. Use will preferably be made
of a hydrocarbon organolithium initiator not comprising a
heteroatom. Representative compounds are aliphatic organolithium
compounds, such as ethyllithium, n-butyllithium (n-BuLi),
isobutyllithium, and the like.
[0066] The polymerization is preferably carried out in the presence
of an inert hydrocarbon solvent which can, for example, be an
aliphatic or alicyclic hydrocarbon, such as pentane, hexane,
heptane, isooctane, cyclohexane or methylcyclohexane, or an
aromatic hydrocarbon, such as benzene, toluene or xylene.
[0067] The polymerization can be carried out continuously or
batchwise. The continuous polymerization can be carried out in a
known way in one or more reactors assumed perfectly stirred by a
person skilled in the art. In the case of the polymerization in
several reactors, the number of reactors generally varies from 2 to
15 and preferably from 2 to 9.
[0068] The polymerization is generally carried out at a temperature
varying from 20.degree. C. to 150.degree. C. and preferably from
30.degree. C. to 12.0.degree. C.
[0069] According to an implementation of the continuous process,
the polymerization can advantageously be carried out in several
reactors by controlling and by balancing the conversion in each
reactor. For example, the maintenance in each reactor of an
individual degree of conversion within a range of values which
depends on the theoretical individual degree of conversion,
calculated from the overall degree of conversion at the end of
polymerization divided by the number of reactors, can contribute to
a reduced polydispersity index of at most 1.6 being obtained.
Preferably then, the individual degree of conversion can vary by
more or less 20% from the overall conversion, with respect to this
theoretical value.
[0070] It is known that the conversion in each reactor is
controlled in particular by the temperature, the residence time,
the amount of polar agent and the amount of monomer entering each
reactor.
[0071] The balancing of the conversions in each reactor, as
indicated above, makes it possible to minimize the polydispersity
index.
[0072] According to a continuous implementation of the process, the
polymerization in several reactors in series can advantageously be
carried out by producing a temperature gradient in the range of
temperatures indicated above, so that the temperature in each
reactor is greater than or equal to the temperature of the reactor
which immediately precedes it, the temperature of the final reactor
being strictly greater than the temperature of the first
reactor.
[0073] According to a continuous implementation of the process, the
polymerization in several reactors in series can also
advantageously be carried out with additional injections of
solvents and/or of monomers in at least one other reactor than the
first. These monomers and/or solvents are then purified so that the
proportion of the number of dead chains in the stream at the outlet
of the final polymerization reactor is less than 30%, preferably
less than 10%, of the number of living chains initiated in the
first reactor. The term "dead chains" is understood to mean the
chains of polymers, the propagation of which has been halted by
reaction with impurities and which are no longer reactive at
polymerization outlets.
[0074] These implementations of the continuous polymerization
process in several reactors can be combined with one another.
[0075] It is, of course, also possible to add, at the end of
polymerization, a transmetallation agent in order to modify the
reactivity of the living chain end.
[0076] The living diene elastomer resulting from the polymerization
is subsequently functionalized in order to prepare the modified
diene elastomer according to the invention.
[0077] According to a first alternative form of the preparation of
the modified diene elastomer according to the invention, the linear
diene elastomer functionalized predominantly in the middle of the
chain a) and the star-branched diene elastomer b) are mixed in the
appropriate proportions.
[0078] The linear diene elastomer functionalized predominantly in
the middle of the chain a) can be obtained by reaction of the
living diene elastomer resulting from the polymerization stage with
a coupling agent capable of introducing, in the middle of the
polymer chain, a hydrolysable or nonhydrolysable alkoxysilane group
bearing, if appropriate, a functional group capable of interacting
with a reinforcing filler within a rubber composition, the
alkoxysilane group being bonded to the two branches of the diene
elastomer via the silicon atom.
[0079] The star-branched diene elastomer b) can be obtained in a
way known per se by reaction of the living chain end with a
star-branching agent, that is to say any polyfunctional molecule,
the functional group being any type of chemical group known by a
person skilled in the art to react with a living chain end.
[0080] The mixing of the two elastomers can be carried out in an
inert solvent, for example an aliphatic or alicyclic hydrocarbon,
such as pentane, hexane, heptane, isooctane or cyclohexane, or an
aromatic hydrocarbon, such as benzene, toluene or xylene, which can
be the same as the polymerization solvent. The mixing will then be
carried out at a temperature of between 20.degree. C. and
120.degree. C. and preferably in the vicinity of 30.degree. C. to
110.degree. C.
[0081] According to a second alternative form of the preparation of
the modified diene elastomer according to the invention, the living
diene elastomer resulting from the polymerization stage is
subjected to the reaction of a star-branching agent and to that of
a coupling agent capable of introducing, in the middle of the
polymer chain, a hydrolysable or nonhydrolyzable alkoxysilane group
bearing, if appropriate, a functional group capable of interacting
with a reinforcing filler within a rubber composition, the
alkoxysilane group being bonded to the two branches of the diene
elastomer via the silicon atom.
[0082] The coupling agent which can be used according to these two
alternative forms of the invention can bear an alkoxysilane
functional group, which can be hydrolysed to give a silanol
functional group, or also a non-hydrolysable alkoxysilane
functional group, and optionally another functional group capable
of interacting with a reinforcing filler, the two functional groups
being directly bonded to one another or being bonded via a spacer
group. The other functional group capable of interacting with a
reinforcing filler and the spacer group are as defined above.
[0083] The coupling agent can be represented by the following
formula (I):
##STR00001##
[0084] in which:
[0085] Y is a saturated or unsaturated, cyclic or non-cyclic,
divalent C.sub.1-C.sub.18 aliphatic hydrocarbon radical or divalent
C.sub.6-C.sub.18 aromatic hydrocarbon radical, preferably a linear
or branched, divalent C.sub.1-C.sub.10 aliphatic hydrocarbon
radical, more preferably a linear divalent C.sub.1-C.sub.5
aliphatic hydrocarbon radical and more preferably still the linear
C.sub.2 or C.sub.3 hydrocarbon radical,
[0086] X is a hydrogen atom or a functional group capable of
interacting with a reinforcing filler,
[0087] the R' radicals, which are substituted or unsubstituted and
identical or different, represent a C.sub.1-C.sub.10, indeed even
C.sub.1-C.sub.8, alkyl group, preferably a C.sub.1-C.sub.4 alkyl
group, more preferably methyl and ethyl.
[0088] The functional group capable of interacting with a
reinforcing filler is as defined above.
[0089] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is a protected or unprotected primary amine, a protected or
unprotected secondary amine or a tertiary amine. The nitrogen atom
can then be substituted by two identical or different groups which
can be a trialkylsilyl radical, the alkyl group having from 1 to 4
carbon atoms, or a C.sub.1-C.sub.10, preferably C.sub.1-C.sub.4,
alkyl radical, more preferably a methyl or ethyl radical, or else
the two substituents of the nitrogen form, with the latter, a
heterocycle comprising a nitrogen atom and at least one carbon
atom, preferably from 2 to 6 carbon atoms.
[0090] Mention may be made, for example, as coupling agent, of
(N,N-dialkylaminopropyl)trialkoxysilanes,
(N-alkylaminopropyl)trialkoxysilanes, the secondary amine
functional group of which is protected by a trialkylsilyl group,
and aminopropyltrialkoxysilanes, the primary amine functional group
of which is protected by two trialkylsilyl groups.
[0091] Preferably, the coupling agent can be chosen from
(3-N,N-dimethylaminopropyl)trimethoxysilane,
(3-N,N-dimethylaminopropyl)triethoxysilane,
(3-N,N-diethylaminopropyl)trimethoxysilane,
(3-N,N-diethylaminopropyl)triethoxysilane,
(3-N,N-dipropylaminopropyl)trimethoxysilane,
(3-N,N-dipropylaminopropyl)triethoxysilane,
(3-N,N-dibutylaminopropyl)trimethoxysilane,
(3-N,N-dibutylaminopropyl)triethoxysilane,
(3-N,N-dipentylaminopropyl)trimethoxysilane,
(3-N,N-dipentylaminopropyl)triethoxysilane,
(3-N,N-dihexylaminopropy)trimethoxysilane,
(3-N,N-dihexylaminopropyl)triethoxysilane,
(3-hexamethyleneaminopropyl)trimethoxysilane,
(3-hexamethyleneaminopropyl)triethoxysilane,
(3-morpholinopropyl)trimethoxysilane,
(3-morpholinopropyl)triethoxysilane,
(3-piperidinopropyl)trimethoxysilane or
(3-piperidinopropyl)triethoxysilane. More preferably, the coupling
agent is (3-N,N-dimethylaminopropyl)trimethoxysilane.
[0092] Preferably, the coupling agent can be chosen from
(3-N,N-methyltrimethylsilylaminopropyl)trimethoxysilane,
(3-N,N-methyltrimethylsilylaminopropyl)triethoxysilane,
(3-N,N-ethyltrimethylsilylaminopropyl)trimethoxysilane,
(3-N,N-ethyltrimethylsilylaminopropyl)triethoxysilane,
(3-N,N-propyltrimethylsilylaminopropyl)trimethoxysilane or
(3-N,N-propyltrimethylsilylaminopropyl)triethoxysilane. More
preferably, the coupling agent is
(3-N,N-methyltrimethylsilylaminopropyl)trimethoxysilane.
[0093] Preferably, the coupling agent can be chosen from
(3-N,N-bistrimethylsilylaminopropyl)trimethoxysilane and
(3-N,N-bistrimethylsilylaminopropyl)trimethoxysilane and
(3-N,N-bistrimethylsilylaminopropyl)triethoxysilane. More
preferably, the coupling agent is
(3-N,N-bistrimethylsilylaminopropyl)trimethoxysilane.
[0094] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is an isocyanate functional group. Preferably, the coupling agent
can be chosen from (3-isocyanatopropyl)trimethoxysilane and
(3-isocyanatopropyl)triethoxysilane.
[0095] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is an imine functional group. Preferably, the coupling agent can be
chosen from
N-(1,3-dimethylbutylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine,
N-(1,3-methylethylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(1,3-methylethylidene)-3-(triethoxysilyl)-1-propanamine,
N-ethylidene-3-(trimethoxysilyl)-1-propanamine,
N-ethylidene-3-(triethoxysilyl)-1-propanamine,
N-(1-methylpropylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine,
N-(4-N,N-dimethylaminobenzylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(4-N,N-dimethylaminobenzylidene)-3-(triethoxysilyl)-1-propanamine,
N-(cyclohexylidene)-3-(trimethoxysilyl)-1-propanamine,
N-(cyclohexylidene)-3-(triethoxysilyl)-1-propanamine,
N-(3-trimethoxysilylpropyl)-4,5-dihydroimidazole,
N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole,
N-(3-trimethoxysilylpropyl)-4,5-imidazole or
N-(3-triethoxysilylpropyl)-4,5-imidazole.
[0096] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is a cyano functional group. Preferably, the functionalization
agent can be chosen from (3-cyanopropyl)trimethoxysilane and
(3-cyanopropyl)triethoxysilane.
[0097] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is a protected or unprotected thiol functional group. Mention may
be made, by way of example, of
(S-trialkylsilylmercaptopropyl)trialkoxysilanes and
(S-trialkylsilylmercaptoethyl)trialkoxysilanes. Preferably, the
coupling agent can be chosen from
(S-trimethylsilylmercaptopropyl)trimethoxysilane,
(S-trimethylsilylmercaptopropyl)triethoxysilane,
(S-tert-butyldimethylsilylmercaptopropyl)trimethoxysilane,
(S-tert-dimethylmercaptopropyl)triethoxysilane,
(S-trimethylsilylmercaptoethyl)trimethoxysilane,
(S-trimethylsilylmercaptoethyl)triethoxysilane,
(S-tert-butyldimethylsilylmercaptoethyl)trimethoxysilane or
(S-tert-butyldimethylsilylmercaptoethyl)triethoxysilane.
[0098] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is a carboxylate functional group. Mention may be made, as
carboxylate functional group, of acrylates or methacrylates. Such a
functional group is preferably a methacrylate. Preferably, the
coupling agent can be chosen from
(3-methacryloyloxypropyl)trimethoxysilane and
(3-methacryloyloxypropyl)triethoxysilane.
[0099] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is an epoxide functional group. Preferably, the coupling agent can
be chosen from (2-glycidyloxyethyl)trimethoxysilane,
(2-glycidyloxyethyl)triethoxysilane,
(3-glycidyloxypropyl)trimethoxysilane,
(3-glycidyloxypropyl)triethoxysilane,
2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane or
2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.
[0100] According to an alternative form of the invention, the
functional group capable of interacting with a reinforcing filler
is a protected or unprotected primary phosphine functional group, a
protected or unprotected secondary phosphine functional group or a
tertiary phosphine functional group. Preferably, the coupling agent
can be chosen from
(3-P,P-bistrimethylsilylphosphinopropyl)trimethoxysilane,
(3-P,P-bistrimethylsilylphosphinopropyl)triethoxysilane,
(3-methyltrimethylsilylphosphinopropyl)trimethoxysilane,
(3-methyltrimethylsilylphosphinopropyl)triethoxysilane,
(3-ethyltrimethylsilylphosphinopropyl)trimethoxysilane,
(3-ethyltrimethylsilylphosphinopropyl)triethoxysilane,
(3-dimethylphosphinopropyl)trimethoxysilane,
(3-dimethylphosphinopropyl)triethoxysilane,
(3-diethylphosphinopropyl)trimethoxysilane,
(3-diethylphosphinopropyl)triethoxysilane,
(3-ethylmethylphosphinopropyl)trimethoxysilane,
(3-ethylmethylphosphinopropyl)triethoxysilane,
(3-diphenylphosphinopropyl)trimethoxysilane or
(3-diphenylphosphinopropyl)triethoxysilane.
[0101] The molar ratio of the coupling agent to the initiator of
the living polymer chains varies from 0.30 to 0.80, preferably from
0.40 to 0.65 and more preferably still from 0.45 to 0.55.
[0102] According to the two alternative forms of the preparation of
the modified diene elastomer of the invention, preferably, the
star-branching agents are tin-based or silicon-based agents with a
functionality of greater than 2 which can be represented by the
formulae SnR.sub.1X'.sub.3, SnHX'.sub.3, SnX'.sub.4,
SiR.sub.1X'.sub.3, SiHX'.sub.3, SiX'.sub.4,
SiR.sub.1(OR'.sub.1).sub.3 and Si(OR'.sub.1).sub.4, with R.sub.1
and R'.sub.1 independently being an alkyl, aralkyl or vinyl group
having from 1 to 20 carbon atoms and X' being a halogen.
[0103] According to a specific embodiment of the second alternative
form of the preparation of the modified diene elastomer according
to the invention, the coupling agent and the star-branching agent
are the same compound. According to this specific embodiment, the
functionalization can advantageously be carried out continuously
and in particular according to the procedures described in
Application WO 2015018599 A1.
[0104] According to another embodiment of the second alternative
form of the preparation of the modified diene elastomer according
to the invention, the coupling agent and the star-branching agent
are distinct. According to this specific embodiment, the
functionalization of the living diene elastomer resulting from the
polymerization stage can be carried out at a temperature varying
from 20.degree. C. to 120.degree. C., in the presence, to begin
with, of an appropriate amount of a star-branching agent in order
to star-branch at most 30% by weight of the living diene elastomer.
Then, subsequently, the remaining living chains of the diene
elastomer obtained after the first stage are functionalized by
addition of a coupling agent capable of introducing, in the middle
of the polymer chain, the alkoxysilane group bearing, if
appropriate, a functional group capable of interacting with a
reinforcing filler within a rubber composition and reaction with
this agent.
[0105] According to the alternative forms of the invention
according to which the functionalization agent bears a protected
primary or secondary amine functional group, the synthesis process
can be continued by a stage of deprotection of the primary or
secondary amine. This stage is carried out after the modification
reaction. The chains functionalized by the protected amine group
can, by way of example, be reacted with an acid, a base, a
fluorinated derivative, such as tetrabutylammonium fluoride, a
silver salt, such as silver nitrate, and the like, in order to
deprotect this amine functional group. These different methods are
described in the work "Protective Groups in Organic Synthesis", T.
W. Green and P. G. M. Wuts, Third Edition, 1999. This deprotection
stage can have the effect of hydrolysing all or a portion of the
hydrolysable alkoxysilane functional groups of the modified diene
elastomer in order to convert them into silanol functional
groups.
[0106] According to the alternative forms of the invention
according to which the functionalization agent bears a protected
thiol functional group, the synthesis process can be continued by a
stage of deprotection of the thiol. This stage is carried out after
the modification reaction. The chains functionalized by the
protected thiol group can, by way of example, be reacted with
water, an alcohol or an acid (hydrochloric acid, sulfuric acid,
carboxylic acid). This deprotection stage can have the effect of
hydrolysing all or a portion of the hydrolysable alkoxysilane
functional groups of the modified diene elastomer in order to
convert them into silanol functional groups.
[0107] According to the alternative forms of the invention
according to which the functionalization agent bears a protected
primary or secondary phosphine functional group, the synthesis
process can be continued by a stage of deprotection of the
phosphine. This stage is carried out after the modification
reaction. The chains functionalized by the protected phosphine
group can, by way of example, be reacted with water, an alcohol or
an acid (hydrochloric acid, sulfuric acid, carboxylic acid). This
deprotection stage can have the effect of hydrolysing all or a
portion of the hydrolysable alkoxysilane functional groups of the
modified diene elastomer in order to convert them into silanol
functional groups.
[0108] According to alternative forms of the invention, the
synthesis process can comprise a stage of hydrolysis of the
hydrolysable alkoxysilane functional groups by addition of an
acidic, basic or neutral compound, as described in the document EP
2 266 819 A1. The hydrolysable functional groups are then converted
in all or in part into silanol functional groups.
[0109] The process for the synthesis of the modified diene
elastomer according to the invention can be continued in a way
known per se by the stages of recovery of the modified
elastomer.
[0110] According to alternative forms of this process, these stages
comprise a stripping stage for the purpose of recovering the
elastomer resulting from the prior stages in dry form. This
stripping stage can have the effect of hydrolysing all or a portion
of the hydrolysable alkoxysilane functional groups of the modified
diene elastomer in order to convert them into silanol functional
groups. Advantageously, at least 50 mol % to 70 mol % of the
functional groups can thus be hydrolysed.
[0111] The modified diene elastomer in accordance with the
invention exhibits a satisfactory resistance to flow, which induces
good behaviour during the storage and transportation of this
rubber.
[0112] The modified diene elastomer according to the invention can
be advantageously used, for a tire application, in a rubber
composition reinforced with at least one inorganic filler, such as
silica, the raw processing/hysteresis compromise of which it
improves. This rubber composition is also the subject-matter of the
invention.
[0113] Thus, as explained above, another subject-matter of the
invention is a reinforced rubber composition based on at least one
reinforcing filler and on an elastomer matrix comprising at least
one modified diene elastomer as described above. It should be
understood that the rubber composition can comprise one or more of
these modified diene elastomers according to the invention.
[0114] The reinforced rubber composition according to the invention
can be provided in the crosslinked state or in the non-crosslinked,
in other words crosslinkable, state.
[0115] The modified diene elastomer according to the invention can,
according to different alternative forms, be used alone in the
composition or as a blend with at least one other conventional
diene elastomer, whether or not star-branched, coupled or
functionalized. Preferably, this other diene elastomer used in the
invention is selected from the group of highly unsaturated diene
elastomers consisting of polybutadienes (BRs), synthetic
polyisoprenes (IRs), natural rubber (NR), butadiene copolymers,
isoprene copolymers and the mixtures of these elastomers. Such
copolymers are more preferably selected from the group consisting
of butadiene/styrene copolymers (SBRs), isoprene/butadiene
copolymers (BIRs), isoprene/styrene copolymers (SIRS) and
isoprene/butadiene/styrene copolymers (SBIRs). It is also possible
to envisage a blend with any synthetic elastomer other than a diene
elastomer, indeed even with any polymer other than an elastomer,
for example a thermoplastic polymer.
[0116] When the conventional elastomer used in blending is natural
rubber and/or one or more diene polymers, such as, for example,
polybutadienes, polyisoprenes or butadiene/styrene or
butadiene/styrene/isoprene copolymers, this elastomer or these
elastomers, modified or unmodified, can then be present at from 1
to 70 parts by weight per 100 parts of modified diene elastomer
according to the invention.
[0117] It should be noted that the improvement in the properties of
the composition according to the invention will be greater as the
proportion of the elastomer(s) different from the modified diene
elastomers of the invention in this composition becomes lower.
[0118] Thus, preferably, the elastomer matrix predominantly
comprises by weight the modified diene elastomer according to the
invention.
[0119] More preferably, the elastomer matrix is composed solely of
the modified diene elastomer according to the invention.
[0120] The rubber composition of the invention comprises, besides
at least one elastomer matrix as described above, at least one
reinforcing filler.
[0121] Use may be made of any type of reinforcing filler known for
its abilities to reinforce a rubber composition which can be used
in the manufacture of tire treads, for example carbon black, a
reinforcing inorganic filler, such as silica, with which is
combined, in a known way, a coupling agent, or also a mixture of
these two types of filler.
[0122] All carbon blacks, used individually or in the form of
mixtures, in particular blacks of the HAF, ISAF or SAF type,
conventionally used in the treads of tires ("tire-grade" blacks)
are suitable as carbon blacks. Mention will more particularly be
made, among the latter, of the reinforcing carbon blacks of the
100, 200 or 300 series (ASTM grades), such as, for example, the
N115, N134, N234, N326, N330, N339, N347 or N375 blacks.
[0123] "Reinforcing inorganic filler" should be understood, in the
present patent application, by definition, as any inorganic or
mineral filler, whatever its colour and its origin (natural or
synthetic), capable of reinforcing by itself alone, without means
other than an intermediate coupling agent, a rubber composition
intended for the manufacture of tires; such a filler is generally
characterized, in a known way, by the presence of hydroxyl (--OH)
groups at its surface.
[0124] Mineral fillers of the siliceous type, in particular silica
(SiO.sub.2), or of the aluminous type, in particular alumina
(Al.sub.2O.sub.3), are especially suitable as reinforcing inorganic
fillers. The silica used can be any reinforcing silica known to a
person skilled in the art, in particular any precipitated or fumed
silica exhibiting a BET specific surface and a CTAB specific
surface both of less than 450 m.sup.2/g, preferably from 30 to 400
m.sup.2/g and in particular between 60 and 300 m.sup.2/g. Mention
will also be made of mineral fillers of the aluminous type, in
particular alumina (Al.sub.2O.sub.3) or aluminium (oxide)
hydroxides, or also reinforcing titanium oxides, for example
described in U.S. Pat. No. 6,610,261 and U.S. Pat. No. 6,747,087.
Also suitable as reinforcing fillers are reinforcing fillers of
another nature, in particular carbon black, provided that these
reinforcing fillers are covered with a siliceous layer or else
comprise, at their surface, functional sites, in particular
hydroxyl sites, requiring the use of a coupling agent in order to
establish the bond between the filler and the elastomer. By way of
example, mention may be made, for example, of carbon blacks for
tires, such as described, for example, in patent documents WO
96/37547 and WO 99/28380.
[0125] The physical state in which the reinforcing inorganic filler
is provided is not important, whether it is in the form of a
powder, of micropearls, of granules, of beads or any other
appropriate densified form. Of course, the term "reinforcing
inorganic filler" is also understood to mean mixtures of different
reinforcing fillers, in particular of highly dispersible siliceous
fillers as described above.
[0126] Preferably, the content of total reinforcing filler (carbon
black and/or other reinforcing filler, such as silica) is between
10 and 200 phr, more preferably between 30 and 150 phr and more
preferably still between 70 and 130 phr, the optimum being, in a
known way, different according to the specific applications
targeted.
[0127] According to an alternative form of the invention, the
reinforcing filler is predominantly other than carbon black, that
is to say that it comprises more than 50% by weight of the total
weight of the reinforcing filler of one or more tillers other than
carbon black, in particular a reinforcing inorganic filler, such as
silica, indeed even it consists exclusively of such a filler.
[0128] According to this alternative form, when carbon black is
also present, it can be used at a content of less than 20 phr, more
preferably of less than 10 phr (for example between 0.5 and 20 phr,
in particular from 1 to 10 phr).
[0129] According to another alternative form of the invention, use
is made of a reinforcing filler predominantly comprising carbon
black and optionally silica or another inorganic filler.
[0130] When the reinforcing filler comprises a filler requiring the
use of a coupling agent in order to establish the bond between the
filler and the elastomer, the rubber composition according to the
invention in addition conventionally comprises an agent capable of
effectively providing this bond. When silica is present in the
composition as reinforcing filler, use may be made, as coupling
agents, of organosilanes, in particular alkoxysilane polysulfides
or mercaptosilanes, or else of at least bifunctional
polyorganosiloxanes.
[0131] Such a coupling agent should not be confused with the
coupling agent used for the synthesis of the modified diene
elastomer described above.
[0132] In the composition according to the invention, the content
of coupling agent is advantageously less than 20 phr, it being
understood that it is generally desirable to use as little of it as
possible. Its content is preferably between 0.5 and 12 phr. The
presence of the coupling agent depends on the presence of the
reinforcing inorganic filler. Its content is easily adjusted by a
person skilled in the art according to the content of this filler;
it is typically of the order of 0.5% to 15% by weight, with respect
to the amount of reinforcing inorganic filler other than carbon
black.
[0133] The rubber composition according to the invention can also
comprise, in addition to the coupling agents, coupling activators,
agents for covering the fillers or more generally processing aids
capable, in a known way, by virtue of an improvement in the
dispersion of the filler in the rubber matrix and of a lowering of
the viscosity of the composition, of improving its ability to be
processed in the raw state, these agents being, for example,
hydrolysable silanes, such as alkylalkoxysilanes, polyols,
polyethers, primary, secondary or tertiary amines, or hydroxylated
or hydrolysable polyorganosiloxanes.
[0134] The rubber compositions in accordance with the invention can
also contain reinforcing organic fillers which can replace all or a
portion of the carbon blacks or of the other reinforcing inorganic
fillers described above. Mention may be made, as examples of
reinforcing organic fillers, of functionalized polyvinyl organic
fillers, such as described in Applications WO-A-2006/069792,
WO-A-2006/069793, WO-A-2008/003434 and WO-A-2008/003435.
[0135] The rubber composition according to the invention can also
comprise all or a portion of the usual additives generally used in
elastomer compositions intended for the manufacture of tires, such
as, for example, pigments, non-reinforcing fillers, protective
agents, such as antiozone waxes, chemical antiozonants or
antioxidants, antifatigue agents, plasticizing agents, reinforcing
or plasticizing resins, methylene acceptors (for example, phenolic
novolak resin) or methylene donors (for example, HMT or H3M), such
as described, for example, in Application WO 02/10269, a
crosslinking system based either on sulfur or on sulfur donors
and/or on peroxide and/or on bismaleimides, vulcanization
accelerators or vulcanization activators.
[0136] The composition is manufactured in appropriate mixers, using
two successive phases of preparation well known to a person skilled
in the art: a first phase of thermomechanical working or kneading
("non-productive" phase) at high temperature, up to a maximum
temperature of between 110.degree. C. and 190.degree. C.,
preferably between 130.degree. C. and 180.degree. C., followed by a
second phase of mechanical working ("productive" phase) down to a
lower temperature, typically of less than 110.degree. C., for
example between 40.degree. C. and 100.degree. C., during which
finishing phase the crosslinking system is incorporated.
[0137] The process for the preparation of a composition according
to the invention generally comprises:
[0138] (i) the implementation, at a maximum temperature of between
130.degree. C. and 180.degree. C., of a first step of
thermomechanical working of the constituents of the composition
comprising the modified diene elastomer according to the invention
and a reinforcing filler, with the exception of a crosslinking
system, then
[0139] (ii) the implementation, at a temperature lower than the
maximum temperature of the first step, of a second step of
mechanical working during which the crosslinking system is
incorporated.
[0140] This process can also comprise, prior to the implementation
of the abovementioned stages (i) and (ii), the stages of the
preparation of the modified diene elastomer according to the
process described above.
[0141] Another subject-matter of the invention is a semi-finished
article made of rubber for a tire, comprising a rubber composition
according to the invention, which is crosslinkable or crosslinked,
or consisting of such a composition.
[0142] The final composition thus obtained can subsequently be
calendered, for example in the form of a sheet or of a plaque or
also extruded, for example in order to form a rubber profiled
element which can be used as a semi-finished rubber product
intended for the tire.
[0143] Due to the improved hysteresis/raw processing compromise
while maintaining the resistance to flow of the elastomer which
characterizes a reinforced rubber composition according to the
invention, it should be noted that such a composition can
constitute any semi-finished product of the tire and very
particularly the tread, reducing in particular its rolling
resistance.
[0144] A final subject-matter of the invention is thus a tire
comprising a semi-finished article according to the invention, in
particular a tread.
[0145] The abovementioned characteristics of the present invention,
and also others, will be better understood on reading the following
description of several implementational examples of the invention,
given by way of illustration and without limitation.
EXAMPLES
[0146] Measurements and Tests Used
[0147] Size Exclusion Chromatography
[0148] The SEC (Size Exclusion Chromatography) technique makes it
possible to separate macromolecules in solution according to their
size through columns filled with a porous gel. The macromolecules
are separated according to their hydrodynamic volume, the bulkiest
being eluted first.
[0149] Without being an absolute method, SEC makes it possible to
comprehend the distribution of the molar masses of a polymer. The
various number-average molar masses (M.sub.e) and weight-average
molar masses (M.sub.w) can be determined from commercial standards
and the polydispersity index (PI=M.sub.w/M.sub.n) can be calculated
via a "Moore" calibration.
[0150] There is no specific treatment of the polymer sample before
analysis. The latter is simply dissolved in the elution solvent at
a concentration of approximately 1 gl.sup.-1. The solution is then
filtered through a filter with a porosity of 0.45 .mu.m before
injection.
[0151] The apparatus used is a Waters Alliance chromatographic
line. The elution solvent is either tetrahydrofuran or
tetrahydrofuran+1 vol % of diisopropylamine+1 vol % of
triethylamine, the flow rate is 1 mlmin.sup.-1, the temperature of
the system is 35.degree. C. and the analytical time is 30 min. A
set of two Waters columns with the Styragel HT6E trade name is
used. The volume of the solution of the polymer sample injected is
100 .mu.l. The detector is a Waters 2410 differential refractometer
and the software for making use of the chromatographic data is the
Waters Empower system.
[0152] The calculated average molar masses are relative to a
calibration curve produced for SBRs having the following
microstructure: 25% by weight (with respect to the weight of the
polymer) of units of styrene type, 23% by weight (with respect to
the butadiene part) of units of 1,2-type and 50% by weight (with
respect to the butadiene part) of units of trans-1,4-type.
[0153] High-Resolution Size Exclusion Chromatography
[0154] The high-resolution SEC (HR SEC) technique is used to
determine the percentages by weight of the various populations of
chains present in a polymer sample.
[0155] There is no specific treatment of the polymer sample before
analysis. The latter is simply dissolved in the elution solvent at
a concentration of approximately 1 gl.sup.-1. The solution is then
filtered through a filter with a porosity of 0.45 .mu.m before
injection.
[0156] The apparatus used is a Waters Alliance 2695 chromatographic
line. The elution solvent is tetrahydrofuran, the flow rate is 0.2
mlmin.sup.-1 and the temperature of the system is 35.degree. C. A
set of three identical columns in series is used (Shodex, length
300 mm, diameter 8 mm). The number of theoretical plates of the set
of columns is greater than 22 000. The volume of the solution of
the polymer sample injected is 50 .mu.l. The detector is a Waters
2414 differential refractometer and the software for making use of
the chromatographic data is the Waters Empower system.
[0157] The calculated molar masses are relative to a calibration
curve produced for SBRs having the following microstructure: 25% by
weight (with respect to the weight of the polymer) of units of
styrene type, 23% by weight (with respect to the butadiene part) of
units of 1,2-type and 50% by weight (with respect to the butadiene
part) of units of trans-1,4-type.
[0158] Mooney Viscosity
[0159] For the polymers and rubber compositions, the Mooney
viscosities ML.sub.(1+4)100.degree. C. are measured according to
Standard ASTM D-1646.
[0160] Use is made of an oscillating consistometer as described in
Standard ASTMD-1646. The Mooney plasticity measurement is carried
out according to the following principle: the elastomer or the
composition in the raw state (i.e., before curing) is moulded in a
cylindrical chamber heated to 100.degree. C. After preheating for
one minute, the rotor rotates within the test specimen at 2
revolutions/minute and the working torque for maintaining this
movement after rotating for 4 minutes is measured. The Mooney
plasticity ML.sub.(1+4) is expressed in "Mooney unit" (MU, with 1
MU=0.83 Nm).
[0161] The difference between the Mooney viscosity of the
composition and the Mooney viscosity of the elastomer makes it
possible to measure the raw processability or processing. The
smaller this difference, the better the raw processing.
[0162] Differential Calorimetry
[0163] The glass transition temperatures (Tg) of the elastomers are
determined using a differential scanning calorimeter.
[0164] Near-Infrared (NIR) Spectroscopy
[0165] The microstructure of the elastomers is characterized by the
near-infrared (NIR) spectroscopy technique.
[0166] Near-infrared spectroscopy (NIR) is used to quantitatively
determine the content by weight of styrene in the elastomer and
also its microstructure (relative distribution of the 1,2-,
trans-1,4- and cis-1,4-butadiene units). The principle of the
method is based on the Beer-Lambert law generalized for a
multicomponent system. As the method is indirect, it involves a
multivariate calibration [Vilmin, F., Dussap, C. and Coste, N.,
Applied Spectroscopy, 2006, 60, 619-291 performed using standard
elastomers having a composition determined by .sup.13C NMR. The
styrene content and the microstructure are then calculated from the
NIR spectrum of an elastomer film having a thickness of
approximately 730 .mu.m. The spectrum is acquired in transmission
mode between 4000 and 6200 cm.sup.-1 with a resolution of 2
cm.sup.-1 using a Bruker Tensor 37 Fourier-transform near-infrared
spectrometer equipped with an InGaAs detector cooled by the Peltier
effect.
[0167] Intrinsic Viscosity
[0168] The intrinsic viscosity of the elastomers at 25.degree. C.
is determined from 0.1 gdl.sup.-1 solution of elastomer in toluene,
according to the following principle:
[0169] The intrinsic viscosity is determined by the measurement of
the flow time t of the polymer solution and of the flow time
t.sub.0 of the toluene in a capillary tube.
[0170] The flow time of the toluene and the flow time of the 0.1
g.dl.sup.-1 polymer solution are measured in an Ubbelohde tube
(diameter of the capillary 0.46 mm, capacity from 18 to 22 ml)
placed in a bath thermostatically controlled at 25-0.1.degree.
C.
[0171] The intrinsic viscosity is obtained by the following
relationship:
h inh = 1 C ln [ ( t ) ( t o ) ] ##EQU00001##
[0172] with:
[0173] C: concentration of the solution of polymer in toluene in
gdl.sup.-1,
[0174] t: flow time of the solution of polymer in toluene in
seconds,
[0175] t.sub.0: flow time of the toluene in seconds,
[0176] h.sub.inh: intrinsic viscosity expressed in dlg.sup.-1.
[0177] Cold Flow (CF.sub.(1+6)100.degree. C.)
[0178] It is a matter of measuring the weight of elastomer extruded
through a calibrated die over a given time (6 hours) and under
fixed conditions (T=100.degree. C.). The die has a diameter of 6.35
mm and a thickness of 0.5 mm and is located at the bottom and at
the centre of a hollowed-out cylindrical dish with a diameter of 52
mm.
[0179] 40.+-.4 g of elastomer, formed beforehand into a pellet
(thickness of 2 cm and diameter of 52 mm), are placed in this
device. A calibrated piston weighing 1 kg (-5 g) is positioned on
the elastomer pellet. The assembly is subsequently placed in an
oven at 100.degree. C..+-.0.5.degree. C.
[0180] As the conditions are not stabilized during the first hour
in the oven, the product extruded at t=1 hour is cut off and then
discarded.
[0181] The measurement is subsequently continued for 6 hours.+-.5
min, during which the product is left in the oven. On conclusion of
the 6 hours, the sample of product extruded is cut off and then
weighed. The result of the measurement is the weight of elastomer
weighed. The lower this result, the more resistant the elastomer is
to cold flow.
[0182] Determination of the Distribution of the Entities of a
Modified Elastomer
[0183] The method employed is a modelling method already set out in
Patent Application WO 2015/018599 A1 on behalf of the Applicant
Companies and described below.
[0184] 1. Example of the Determination of the Ratio of Kinetic
Constants (K) of the Kinetic Model of Functionalization in a
Batchwise Stirred Reactor
[0185] Experimental Determination of the Percentage by Weight of
the Chains Functionalized at the Chain End, of the Chains
Functionalized in the Middle of the Chain and of the Star-Branched
(3 Branches) Chains and of the Jump in Viscosity as a Function of
the (3-N,N-dimethylaminopropyl)trimethoxysilane/n-BuLi Molar
Ratio
[0186] 91.6 ml (70.5 g) of methylcyclohexane, 14.8 ml (9.65 g) of
butadiene and 0.49 ml of a 0.078 moll.sup.-1 solution of
tetrahydrofurfuryl ether in methylcyclohexane are introduced into
eleven 250 ml glass bottles (Steinie bottles). After neutralization
of the impurities in the solution to be polymerized by addition of
n-butyllithium (n-BuLi), 1.90 ml of 0.097 moll.sup.-1 n-BuLi in
methylcyclohexane are added. The polymerization is carried out at
60.degree. C.
[0187] After 15 minutes, the degree of conversion of monomer
reaches 95%. This content is determined by weighing an extract
dried at 140.degree. C. under a reduced pressure of 200 mmHg. A
control bottle (bottle No. 1) is stopped with an excess of methanol
with respect to the lithium. The "initial" intrinsic viscosity is
0.66 dlg.sup.-1. 0.88 ml of a 0.1 moll.sup.-1 solution of
(3-N,N-dimethylaminopropyl)trimethoxysilane in methylcyclohexane is
added to the solutions of living polymer (0.48 molar eq. vs Li)
present in bottles 2 to 9, 0.73 ml of this same solution is added
to bottle 10 (0.40 molar eq. vs Li) and 1.83 ml of this same
solution are added to bottle 11 (1.0 molar eq. vs Li). After
reacting at 60.degree. C. for 15 minutes, the solutions are
antioxidized by addition of 0.4 part per hundred parts of elastomer
(phr) of 4,4'-methylenebis(2,6-di(tert-butyl)phenol) and 0.2 part
per hundred parts of elastomer (phr) of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. The polymers
thus treated are separated from their solution by drying at
60.degree. C. under reduced pressure and a nitrogen stream for 12
hours.
[0188] The "final" intrinsic viscosities, the jumps in viscosity,
defined as the ratios of the "final" intrinsic viscosities to the
"initial" intrinsic viscosity, and also the percentages by weight
of the deactivated chains (P), of the chains functionalized at the
chain end (PA), of the chains functionalized in the middle of the
chain (P.sub.2A) and of the star-branched chains (P.sub.3A) are
presented in Table 1 below.
TABLE-US-00001 TABLE 1 Change in the distribution of the entities P
+ PA/P.sub.2A/P.sub.3A and in the jump in viscosity as a function
of the (3-N,N- dimethylaminopropyl)trimethoxysilane/n-BuLi molar
ratio (3-N,N- Dimethylaminopropyl) trimethoxysilane/Li Jump in P +
PA/P.sub.2A/P.sub.3A Bottle molar ratio viscosity (wt. %) 2 0.48
12/77/10 3 0.48 13/77/9 4 0.48 13/78/9 5 0.48 13/82/5 6 0.48
13/83/5 7 0.48 13/83/4 8 0.48 14/83/4 9 0.48 1.54 11/84/4 10 0.40
1.61 15/53/25 11 1.00 1.09 72/20/7
[0189] The living diene elastomer is functionalized according to
the reaction mechanism:
TABLE-US-00002 Reaction Mechanism R1 PLi + A .sup.k.sub.1fi PA R2
PLi + PA .sup.k.sub.2fi P.sub.2A R3 PLi + P.sub.2A .sup.k.sub.3fi
P.sub.3A
[0190] where [0191] A represents the functionalization agent,
[0192] represents a living elastomer chain, [0193] PA represents
the elastomer functionalized at the chain end, [0194] P.sub.2A
represents the coupled elastomer, [0195] P.sub.3A represents the
star-branched elastomer comprising three branches, and [0196]
k.sub.i represents the kinetic constant of the reaction Ri,
[0197] being carried out according to the following rate law:
TABLE-US-00003 Reactions Reaction rate R1 V.sub.1 = k.sub.1 |PLi]
|A] R2 V.sub.2 = k.sub.2 |PLi] |PA] R3 V.sub.3 = k.sub.3 |PLi]
|P.sub.2A]
[0198] where [0199] k.sub.1, k.sub.2 and k.sub.3 are the kinetic
constants respectively of the reactions R1, R2 and R3 (expressed in
(m.sup.3/mol)s.sup.-1), [0200] [PLi] is the concentration of living
chains (expressed in mol/m.sup.3), [0201] [A] is the concentration
of modification agent A (expressed in mol/m.sup.3), [0202] [PA] is
the concentration of elastomer functionalized at the chain end
(expressed in mol/m.sup.3), [0203] [P.sub.2A] is the concentration
of coupled elastomer (expressed in mol/m.sup.3), [0204] [P.sub.3A]
is the concentration of star-branched elastomer comprising three
branches (expressed in mol/m.sup.3), [0205] the ratio K of the
kinetic constants defined as:
[0205] K = k 1 k 2 = k 2 k 3 ##EQU00002##
[0206] being greater than 1.
[0207] The kinetic model for functionalization incorporated,
according to a person skilled in the art, in a perfectly stirred
batchwise reactor model (bibliography: Villermeaux, J; Genie de la
reaction chimique; 1993) makes it possible to determine the
distribution of the different entities. Furthermore, the chains can
be deactivated (P) during the polymerization and/or
functionalization stage. Thus, the final product is a mixture of
deactivated elastomer (P), elastomer functionalized at the chain
end (PA), elastomer functionalized in the middle of the chain
(P.sub.2A) and star-branched elastomer (P.sub.3A).
[0208] For the experimental points of Table 1 above, the value of
K=10.sup.2.+-.1 was estimated according to the description of the
perfectly stirred batchwise reactor model, which represents the
reactor used for these experiments.
[0209] The distribution of the entities P, PA, P.sub.2A and
P.sub.3A as a function of the functionalization agent/living
polymer chains (PLi) molar ratio is represented in FIG. 1:
simulated (lines) and measured (points).
[0210] 2. Example of the Determination of the Kinetics of
Functionalization in a Batchwise Stirred Reactor
[0211] Experimental Determination of the Percentage by Weight of
the Chains Functionalized at the Chain End, of the Chains
Functionalized in the Middle of the Chain and of the Star-Branched
(3 Branches) Chains as a Function of the Coupling Time with
(3-N,N-dimethylaminopropyl)trimethoxysilane (.about.0.5 mol eq. vs
Li)
[0212] 91.6 ml (70.5 g) of methylcyclohexane, 14.8 ml (9.65 g) of
butadiene and 0.49 ml of a 0.078 moll.sup.-1 solution of
tetrahydrofurfuryl ether in methylcyclohexane are introduced into
twenty-two 250 ml glass bottles (Steinie bottles). After
neutralization of the impurities in the solution to be polymerized
by addition of n-butyllithium (n-BuLi), 1.90 ml of 0.097
moll.sup.-1 n-BuLi in methylcyclohexane are added. The
polymerization is carried out at 60.degree. C.
[0213] After 15 minutes, the degree of conversion of monomer
reaches 95%. This content is determined by weighing an extract
dried at 140.degree. C. under a reduced pressure of 200 mmHg. 0.88
ml of a 0.1 moll.sup.-1 solution of
(3-N,N-dimethylaminopropyl)trimethoxysilane in methylcyclohexane
are added to the living polymer solutions (0.48 molar eq. vs Li)
present in the remaining twenty-one bottles. After reacting at
60.degree. C. for 10 seconds (bottles 12, 13 and 14), 15 seconds
(bottles 15, 16 and 17), 20 seconds (bottles 18, 19 and 20), 30
seconds (bottles 21 and 22), 2 minutes (bottle 23) and 15 minutes
(bottles 24, 25, 26, 27, 28, 29, 30, 31 and 32), the solutions are
antioxidized by addition of 0.4 part per hundred parts of elastomer
(phr) of 4,4'-methylenebis(2,6-di(tert-butyl)phenol) and 0.2 part
per hundred parts of elastomer (phr) of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. The polymers
thus treated are separated from their solution by drying at
60.degree. C. under reduced pressure and a nitrogen stream for 12
hours.
[0214] The percentages by weight of the deactivated chains (P), of
the chains functionalized at the chain end (PA), of the chains
functionalized in the middle of the chain (P.sub.2A) and of the
star-branched chains (P.sub.3A) are presented in Table 2 below.
TABLE-US-00004 TABLE 2 Change in the distribution of the entities P
+ PA/P.sub.2A/P.sub.3A as a function of the reaction time with
(3-N,N-dimethylaminopropyl)trimethoxysilane Reaction time with
(3-N,N- dimethylaminopropyl) P + PA P.sub.2A P.sub.3A Bottle
trimethoxysilane (wt. %) (wt. %) (wt. %) 12 10 s 23 76 1 13 10 s 23
76 1 14 10 s 22 77 1 15 15 s 19 79 1 16 15 s 20 79 1 17 15 s 19 79
1 18 20 s 18 81 1 19 20 s 17 81 1 20 20 s 18 81 1 21 30 s 16 82 2
22 30 s 14 83 2 23 2 min 11 86 2 24 15 min 12 77 10 25 15 min 13 77
9 26 15 min 13 78 9 27 15 min 13 82 5 28 15 min 13 83 4 29 15 min
13 83 4 30 15 min 14 83 4 31 15 min 11 84 4 32 15 min 9 88 3
[0215] By using the same kinetic model as the preceding example and
the value of K=10.sup.2.+-.1, the value of k.sub.1[PLi], in the
kinetic model, is estimated at 10.sup.4.+-.0.2. The simulated
yields are compared with the measured yields as a function of the
reaction time in a perfectly stirred batchwise reactor in FIG.
2.
[0216] 3. Example of the Determination of the Ratio of Kinetic
Constants (K of Functionalization in Continuous Configuration
[0217] A variable amount of functionalization agent is injected
into a continuous pilot-scale polymerization plant, at the outlet
of the continuous stirred polymerization reactor, assumed perfectly
stirred, in order to characterize the section of continuous
functionalization. The functionalization section is composed of a
static mixer of Kenics type comprising 36 4-litre elements and of a
continuous stirred reactor with a volume of 32.5 litres, assumed
perfectly stirred. The minimum residence time in the stirred
reactors is 20 minutes.
[0218] Methyl cyclohexane, butadiene, styrene and
tetrahydrofurfuryl ethyl ether are continuously introduced
according to the following proportions: butadiene flow rate by
weight=2.85 kgh.sup.-1, styrene flow rate by weight=1.25
kgh.sup.-1, concentration by weight of monomer=11 wt. %, 60 ppm of
tetrahydrofurfuryl ethyl ether, into a 32.5-litre continuous
stirred reactor, assumed perfectly stirred according to a person
skilled in the art. n-Butyllithium (n-BuLi) is introduced in a
sufficient amount in order to neutralize the protic impurities
introduced by the different constituents present in the line inlet.
850 .mu.mol of n-BuLi per 100 g of monomers are introduced at the
inlet of the reactor.
[0219] The different flow rates are calculated in order for the
mean residence time in the reactor to be 40 min. The temperature is
maintained at 90.degree. C.
[0220] The degree of conversion, measured on a sample withdrawn at
the reactor outlet, is 92.6%.
[0221] At the outlet of the polymerization reactor,
(3-N,N-dimethylaminopropyl)trimethoxysilane in solution in
methylcyclohexane is added to the living polymer solution in
different amounts (different
(3-N,N-dimethylaminopropyl)trimethoxysilane/PLi molar ratios) in
order to characterize the functionalization process. This solution
is mixed in a static mixer composed of 36 mixing elements of Kenics
KMR type and then passes through an empty pipe, the total residence
time in the pipe being 3 minutes (static mixer+empty pipe), and a
32.5-litre continuous stirred reactor, assumed perfectly stirred
according to a person skilled in the art, with a residence time of
40 minutes. The polymers are subsequently subjected to an
antioxidizing treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.
[0222] The polymers thus treated are separated from their solution
by a steam stripping operation and then dried on an open mill at
100.degree. C.
[0223] The jumps in intrinsic viscosity (JV) measured for the
elastomers with a PI of the order of 2 are presented in FIG. 3.
[0224] The kinetic model of functionalization described above is
incorporated, according to a person skilled in the art, in a model
of tubular reactor (representative of the Kenics static mixer),
followed by a perfectly stirred continuous reactor (representative
of the stirred functionalization reactor) (bibliography:
Villermeaux, J; Genie de la reaction chimique; 1993) and makes it
possible to determine the distribution of PLi, P, PA, P.sub.2A and
P.sub.3A entities.
[0225] In order to make the connection between the distribution of
the entities PLi, P, PA, P.sub.2A and P.sub.3A which is calculated
by the kinetic model of functionalization and the experimental
ratio of intrinsic viscosities before and after functionalization
(JV), the JV is calculated theoretically by the equation below:
JV = ( i = 1 n w P i A M _ w , P i A a g i ' M _ w , P a )
##EQU00003##
[0226] where:
[0227] w.sub.PiA is the fraction by weight of the entities
P.sub.iA, PLi and P;
[0228] M.sub.w is the weight-average molecular weight;
[0229] a is the parameter of the MHS (Mark-Houwink-Sakurada)
equation and is equal to 0.75;
[0230] g.sub.i' is a correction for the star-branched polymers, for
example:
g i ' = ( 3 i - 2 i 2 ) b ##EQU00004##
[0231] where:
[0232] b is equal to 0.58 (work: Structure and Rheology of Molten
Polymers),
[0233] By assuming that the residence time is long enough to be
regarded as infinite, the ratio of kinetic constants K is estimated
by minimizing the differences in experimental and calculated JV.
The value of K is 10.sup.1.+-.1, as represented in FIG. 3.
[0234] The calculated JV for elastomers exhibiting a PI of the
order of 1.5 is also represented in FIG. 3.
[0235] The calculated JV is determined from the distribution of
entities which is calculated by the kinetic model incorporated in
the models of tubular and perfectly stirred continuous reactors
(FIG. 4).
[0236] Dynamic Properties
[0237] The dynamic properties and in particular tan .delta. max are
measured on a viscosity analyser (Metravib VA4000) according to
Standard ASTM D 5992-96. The response of a sample of vulcanized
composition (cylindrical test specimen with a thickness of 2 mm and
a cross-section of 79 mm.sup.2), subjected to a simple alternating
sinusoidal shear stress, at a frequency of 10 Hz, under standard
temperature conditions (40.degree. C.) according to Standard ASTM D
1349-99, is recorded. A strain amplitude sweep is carried out from
0.1% to 50% peak-to-peak (outward cycle) and then from 50% to 0.1%
peak-to-peak (return cycle). The result more particularly made use
of is the loss factor tan .delta.. For the return cycle, the
maximum value of tan .delta. observed, denoted tan .delta. max, is
indicated. This value is representative of the hysteresis of the
material and in the present case of the rolling resistance: the
smaller the value of tan .delta. max, the lower the rolling
resistance. In the examples, the results of the dynamic properties
are given in base 100. The higher this number expressed in base
100, the lower the hysteresis.
[0238] Preparation of the Polymers
[0239] Preparation of the Polymer A: SBR
aminoalkoxysilane-Functional in the Middle of the Chain According
to the Invention
[0240] Methylcyclohexane, butadiene, styrene and tetrahydrofurfuryl
ethyl ether are continuously introduced into two fed 14-1 reactors
arranged in series, assumed perfectly stirred according to a person
skilled in the art, according to the following proportions:
butadiene flow rate by weight=1.756 kgh.sup.-1 (1.231 kgh.sup.-1 of
which are injected at the inlet of the first reactor and 0.525
kgh.sup.-1 of which are injected between the first and the second
reactor after having been purified on alumina columns), styrene
flow rate by weight=0.906 kgh.sup.-1, total concentration by weight
of monomer in the second reactor=12.5 wt. %, tetrahydrofurfuryl
ethyl ether flow rate by weight=134 gh.sup.-1.
[0241] n-Butyllithium (n-BuLi) is introduced in a sufficient amount
in order to neutralize the protic impurities introduced by the
different constituents present in the inlet of the first reactor.
720 .mu.mol of n-BuLi per 100 g of monomer are introduced at the
inlet of the first reactor.
[0242] The different flow rates are calculated in order for the
mean residence time in the final reactor to be 30 min. The two
reactors in series are respectively maintained at the following
temperatures: 58.degree. C. for the first and 85.degree. C.' for
the second.
[0243] A sample of polymer solution is withdrawn at the outlet of
the second polymerization reactor. The polymer thus obtained is
subjected to an antioxidizing treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine. The polymer thus
treated is subsequently separated from its solution by a steam
stripping operation and then dried on an open mill at 100.degree.
C. The "initial" intrinsic viscosity measured is 1.42 dlg.sup.-1.
The number-average molar mass M.sub.n, determined by the SEC
technique, is 97 000 gmol.sup.-1 and the polydispersity index PI is
1.50.
[0244] At the outlet of the second polymerization reactor, 385
.mu.mol per 100 g of monomer of
(3-N,N-dimethylaminopropyl)trimethoxysilane (coupling and
star-branching agent CA) in solution in methylcyclohexane are added
to the solution of living polymer (CA/Li=0.53). This solution is
mixed in a static mixer composed of 36 mixing elements of Kenics
KMR type and in a 14-litre continuous stirred reactor, assumed
perfectly stirred by a person skilled in the art, with a residence
time of 30 minutes.
[0245] The polymer thus obtained is subjected to an antioxidizing
treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-(test-butyl)phenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.
[0246] The polymer thus treated is subsequently separated from its
solution by a steam stripping operation and then dried on an open
mill at 100.degree. C.
[0247] The "final" intrinsic viscosity measured is 1.91 dlg.sup.-1.
The jump in viscosity, defined as the ratio of the "final"
viscosity to the "initial" viscosity, is in this instance 1.34.
[0248] The Mooney viscosity of this polymer A is 70.
[0249] The number-average molar mass M.sub.n, determined by the SEC
technique, is 165 000 gmol.sup.-1 and the polydispersity index PI
is 1.45.
[0250] The microstructure of this polymer is determined by the NIR
method. The content of 1,2-units is 23.1%, with respect to the
butadiene units. The content by weight of styrene is 27.7%.
[0251] The glass transition temperature of this polymer is
-49.degree. C.
[0252] The cold flow CF.sub.(1+6)100.degree. C. of the polymer is
2.1.
[0253] The distribution of the entities after functionalization is
given with the modelling method described above: 87% of functional
chains, 77% of which are functional in the middle of the chain, and
13% of star-branched chains.
[0254] Preparation of the Polymer B: SBR
aminoalkoxysilane-Functional in the Middle of the
Chain--Comparative
[0255] Methylcyclohexane, butadiene, styrene and tetrahydrofurfuryl
ethyl ether are continuously introduced according to the following
proportions: butadiene flow rate by weight=1.22 kgh.sup.-1, styrene
flow rate by weight=0.536 kgh.sup.-1, concentration by weight of
monomer=11 wt. %, 60 ppm of tetrahydrofurfuryl ethyl ether, into a
stirred continuously fed 14-1 reactor, assumed perfectly stirred
according to a person skilled in the art. n-Butyllithium (n-BuLi)
is introduced in a sufficient amount in order to neutralize the
protic impurities introduced by the different constituents present
in the inlet of the first reactor. 929 .mu.mol of n-BuLi per 100 g
of monomer are introduced at the inlet of the reactor.
[0256] The different flow rates are calculated in order for the
mean residence time in the reactor to be 40 min. The temperature is
maintained at 90.degree. C.
[0257] A sample of polymer solution is withdrawn at the outlet of
the polymerization reactor. The polymer thus obtained is subjected
to an antioxidizing treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. The polymer
thus treated is subsequently separated from its solution by a steam
stripping operation and then dried on an open mill at 100.degree.
C. The "initial" intrinsic viscosity measured is 1.42 dlg.sup.-1.
The number-average molar mass M.sub.n, determined by the SEC
technique, is 80 000 gmol.sup.-1 and the polydispersity index PI is
1.90 (which does not comply with the definition of the modified
diene elastomers according to the invention).
[0258] At the outlet of the polymerization reactor, 474 .mu.mol per
100 g of monomer of (3-N,N-dimethylaminopropyl)trimethoxysilane
(coupling and star-branching agent CA) in solution in
methylcyclohexane are added to the solution of living polymer
(CA/Li=0.51). This solution is mixed in a static mixer composed of
36 mixing elements of Kenics KMR type and in a 14-litre continuous
stirred reactor, assumed perfectly stirred by a person skilled in
the art, with a residence time of 40 minutes.
[0259] The polymer thus obtained is subjected to an antioxidizing
treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine.
[0260] The polymer thus treated is subsequently separated from its
solution by a steam stripping operation and then dried on an open
mill at 100.degree. C.
[0261] The "final" intrinsic viscosity measured is 1.90 dlg.sup.-1.
The jump in viscosity, defined as the ratio of the "final"
viscosity to the "initial" viscosity, is in this instance 1.30.
[0262] The Mooney viscosity of this polymer B is 56.
[0263] The number-average molar mass M.sub.n, determined by the SEC
technique, is 135 000 gmol.sup.-1 and the polydispersity index PI
is 1.72.
[0264] The microstructure of this polymer is determined by the NIR
method. The content of 1,2-units is 24.5%, with respect to the
butadiene units. The content by weight of styrene is 27.5%.
[0265] The glass transition temperature of this polymer is
-47.degree. C.
[0266] The cold flow CF.sub.(1+6)100.degree. C. of the polymer is
1.6.
[0267] The distribution of the entities after functionalization is
given with the modelling method described above: 84% of functional
chains, 77% of which are functional in the middle of the chain, and
16% of star-branched chains.
[0268] Preparation of the Polymer C: SBR
aminoalkoxysilane-Functional in the Middle of the
Chain--Comparative
[0269] Methylcyclohexane, butadiene, styrene and tetrahydrofurfuryl
ethyl ether are continuously introduced into two stirred
continuously fed 14-1 reactors arranged in series, assumed
perfectly stirred according to a person skilled in the art,
according to the following proportions: butadiene flow rate by
weight=1.756 kgh.sup.-1 (1.231 kgh.sup.-1 of which are injected at
the inlet of the first reactor and 0.525 kgh.sup.-1 of which are
injected between the first and the second reactor after having been
purified on alumina columns), styrene flow rate by weight=0.906
kgh.sup.-1, total concentration by weight of monomer in the second
reactor=12.5 wt. %, tetrahydrofurfuryl ethyl ether flow rate by
weight=134 g/h.
[0270] n-Butyllithium (n-BuLi) is introduced in a sufficient amount
in order to neutralize the protic impurities introduced by the
different constituents present at the inlet of the first reactor.
555 .mu.mol of n-BuLi per 100 g of monomer are introduced at the
inlet of the first reactor.
[0271] The different flow rates are calculated in order for the
mean residence time in the final reactor to be 30 min. The two
reactors in series are respectively maintained at the following
temperatures: 58.degree. C. for the first and 85.degree. C. for the
second.
[0272] A sample of polymer solution is withdrawn at the outlet of
the second polymerization reactor. The polymer thus obtained is
subsequently subjected to an antioxidizing treatment with addition
of 0.4 phr of 2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and
0.2 phr of N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine. The
polymer thus treated is subsequently separated from its solution by
a steam stripping operation and then dried on an open mill at
100.degree. C. The "initial" intrinsic viscosity measured is 1.69
dlg.sup.-1. The number-average molar mass M.sub.n, determined by
the SEC technique, is 133 000 gmol.sup.-1 and the polydispersity
index PI is 1.45.
[0273] At the outlet of the polymerization reactor, 305 .mu.mol per
100 g of monomer of (3-N,N-dimethylaminopropyl)trimethoxysilane
(coupling and star-branching agent CA) in solution in
methylcyclohexane are added to the solution of living polymer
(CA/Li=0.55). This solution is mixed in a static mixer composed of
36 mixing elements of Kenics KMR type and in a 14-litre continuous
stirred reactor, assumed perfectly stirred by a person skilled in
the art, with a residence time of 30 minutes.
[0274] The polymer thus obtained is subsequently subjected to an
antioxidizing treatment with addition of 0.4 phr of
2,2'-methylenebis(4-methyl-6-(tert-butyl)phenol) and 0.2 phr of
N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine.
[0275] The polymer thus treated is subsequently separated from its
solution by a steam stripping operation and then dried on an open
mill at 100.degree. C.
[0276] The "final" intrinsic viscosity measured is 2.23 dlg.sup.-1.
The jump in viscosity, defined as the ratio of the "final"
viscosity to the "initial" viscosity, is in this instance 1.32.
[0277] The Mooney viscosity of this polymer C is 118 (which does
not comply with the definition of the invention).
[0278] The number-average molar mass M.sub.n, determined by the SEC
technique, is 224 700 gmol.sup.-1 and the polydispersity index PI
is 1.40.
[0279] The microstructure of this polymer is determined by the NIR
method. The content of 1,2-units is 23.4%, with respect to the
butadiene units. The content by weight of styrene is 27.7%.
[0280] The glass transition temperature of this polymer is
-48.degree. C.
[0281] The cold flow CF.sub.(1+6)100.degree. C. of the polymer is
0.26.
[0282] The distribution of the entities after functionalization is
given with the modelling method described above: 90% of functional
chains, 76% of which are functional in the middle of the chain, and
10% of star-branched chains.
[0283] Comparative Examples of Rubber Compositions
[0284] Three compositions given in Table 3 below are compared.
Composition 1 is in accordance with the invention. Compositions 2
and 3 are comparative compositions not in accordance with the
invention.
[0285] The formulations are expressed in percentage by weight per
100 parts by weight of elastomer (phr).
TABLE-US-00005 TABLE 3 Comparative Example Examples Composition 1 2
3 Polymer A 100 Polymer B 100 Polymer C 100 Silica (1) 80 80 80
N234 3 3 3 Resin Tg = 52.degree. C. 40 40 40 Coupling agent (2) 6.4
6.4 6.4 ZnO 0.9 0.9 0.9 Stearic acid 3 3 3 Antioxidant (3) 2.2 2.2
2.2 Diphenylguanidine 1.6 1.6 1.6 Sulfur 1 1 1 Sulfenamide (4) 2.3
2.3 2.3 (1) Silica, Zeosil 1165MP from Rhodia (2) Si69 from Degussa
(3) N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (4)
N-Cyclohexyl-2-benzothiazolesulfenamide
[0286] The following procedure is used for the tests which
follow:
[0287] Each of the compositions is produced, in a first step, by
thermomechanical working and then, in a second finishing step, by
mechanical working.
[0288] The elastomer, two-thirds of the silica, the coupling agent,
the diphenylguanidine and the carbon black are introduced into a
laboratory internal mixer of "Banbury" type which has a capacity of
400 cm.sup.3, which is 72% filled and which has an initial
temperature of 90.degree. C.
[0289] The thermomechanical working is carried out by means of
blades, the mean speed of which is 50 rev/min and the temperature
of which is 90.degree. C.
[0290] After one minute, the final one-third of the silica, the
antioxidant, the stearic acid, the antiozone wax, the MES oil and
the resin are introduced, still under thermomechanical working.
[0291] After two minutes, the zinc oxide is introduced, the speed
of the blades being 50 rev/min.
[0292] The thermomechanical working is carried out for a further
two minutes, up to a maximum dropping temperature of approximately
160.degree. C.
[0293] The mixture thus obtained is recovered and cooled and then,
in an external mixer (homofinisher), the sulfur and the sulfenamide
are added at 30.degree. C., the combined mixture being further
mixed for a time of 3 to 4 minutes (second step of mechanical
working).
[0294] The compositions thus obtained are subsequently calendered,
either in the form of plaques (with a thickness ranging from 2 to 3
mm) or thin sheets of rubber, for the measurement of their physical
or mechanical properties, or in the form of profiled elements which
can be used directly, after cutting and/or assembling to the
desired dimensions, for example as semi-finished products for
tires, in particular for treads.
[0295] Crosslinking is carried out at 150.degree. C. for 40
min.
[0296] The results are presented in Table 4.
TABLE-US-00006 TABLE 4 Rubber results (Tan .delta. max 40.degree.
C., ML.sub.(1+4)100.degree. C. composition, Cold flow): Comparative
Example Examples Composition 1 2 3 Polymer A B C ML.sub.(1+4)
100.degree. C. elastomer 70 56 118 Tan .delta. max 40.degree. C.
100 101 100 ML.sub.(1+4) 100.degree. C. composition 80 75 NM*
ML.sub.(1+4)100.degree. C. composition - 10 19 --
ML.sub.(1+4)100.degree. C. elastomer Cold flow (g/6 h) 2.10 1.66
0.26 *Value not measurable as too high.
[0297] The results presented in Table 4 show an equivalent
hysteresis between the composition 1 according to the invention in
comparison with that of the control composition 2 (polymer B having
a high polydispersity index before functionalization and
star-branching) and with that of the control composition 3 (polymer
C having a high Mooney viscosity).
[0298] The processability of the composition 1 according to the
invention, which is given by difference between the Mooney
viscosity of the composition and the Mooney viscosity of the
elastomer, is significantly better than that of the control
compositions 2 and 3.
[0299] Finally, the resistance to flow of the composition 1 is
comparable to that of the control composition 2. Thus, the results
presented in Table 4 demonstrate an improvement in the
hysteresis/raw processing compromise of the composition containing
the polymer according to the invention, while maintaining the
resistance to flow of the elastomer.
* * * * *